Railway infrastructure company Network Rail said accounting movements were largely responsible for its reported 51.1% crash in pre-tax profit to £506m (€694m, $782m) over the year to 31 March 2015 compared with the year before.

The company reported a 13.3% fall in operating profit and put the difference down to accounting gains on financial hedges that were recorded over the previous financial year, saying it did not affect the funds available for railway investment.

Network Rail claimed most of the results which appeared disappointing were conscious decisions and did not constitute a threat. The company said that a decision by its regulator that it did not need as much income to manage its business was to blame for the fall in operating profit.

Finance director Patrick Butcher said that the company was happy with the continuing growth in railway popularity and the necessary investments that follow the high demand.

"While progress is being made in improving performance, safety, asset reliability and delivering more renewals and projects, our rate of acceleration in these areas isn't yet where we want it to be," he said.

"With more than a million more trains on the network than 10 years ago, there are inevitable challenges. We are determined to do more to improve and action is being taken to quicken the pace of change."

Network Rail also reported that it had invested a record £3.4bn in the expansion of the British railway system in the last year.